1. Field of the Invention
The invention is directed to an ultrasonic or u/s test device for nondestructive testing of a workpiece moving relative thereto by the pulse echo method.
2. Description of the Prior Art
DE-OS 27 40 106 discloses a u/s test device for nondestructive testing of metallic objects having a test head carrier at which are arranged three test heads whose sound beam axes intersect at a point on the inside of the workpiece and which are outfitted with fluid coupler systems for coupling with the workpiece surface. The test heads are fastened so as to be adjustable at the carrier frame at a distance from one another and a travel path forming a duct is associated with each test head separately. The two outer test heads work according to the pulse echo system, wherein one test head functions as the transmitter and the other functions as the receiver. Since the intensity of the received signal is highly dependent on the surface geometry, the alignment of the two outer test heads corresponding to the surface geometry of the workpiece to be tested must be effected by the third test head arranged between the two outer test heads by means of a sound attenuation measurement.
A disadvantage in this test device consists in that it is restricted to only one type of acoustic irradiation and in the costly electronics required for optimally adjusting the transmitting and receiving test heads. Further, signal processing required for the adjustment of the test heads puts a strain on the testing performance.
A u/s test device for nondestructive testing of welds is known from DE-OS 27 51 810 in which a total of six test heads, whose sound beams intersect at a point, are arranged in a test spider. The sound-transmitting coupling is effected by guiding water into the contact plane. A disadvantage in this arrangement consists in that the coupling medium is supplied to the test device in an uncontrolled manner and the cost for controlling the coupling is accordingly very high. Further, the test performance is very low due to the cyclical interrogation of the individual test heads, since it is always necessary to wait for the echo of the radiated sound pulse first before the next sound pulse can be radiated. Another substantial disadvantage consists in that the test heads are installed in individual holders which change position relative to one another due to tolerances of the test piece or transporting and guidance tolerances.